Posted
by
Soulskill
on Wednesday September 05, 2012 @04:11PM
from the i'll-order-a-dozen dept.

Zothecula writes "Well, Patrick Priebe might have outdone himself with this one. In the past, the German cyberpunk weapons-maker has brought us such creations as a wrist-mounted mini-crossbow, a laser-sighted rotary-saw-blade-shooting crossbow, and a flame-throwing glove. His latest nasty futuristic device? A video game-inspired electromagnetic weapon, called the Gauss Rifle."

Actually the main problem is that to achieve good efficiency the barrel must be very long.Also you need a fast power supply, which is a major problem for any electromagnetic gun.

Ever see those people with their little RC dragsters? One turn of wire armatures with high current draw cells to power them? I think science has this covered by now, it's only a question of how big a projectile you want to lob. The US Navy has been experimenting with these for years and plan to equip ships with them, capable of lobbing shells well over one hundred miles, at mach 5 or better. Power supplies capable of high current draws and perhaps arrays of capacitors and you're well on your way.

It's really got to be caps because batteries are tempermental and can only be recharged so many times and most of them seem to be inherently horrible things to have on fire. They use plenty of batteries, but if you're going to be stacking them up in piles then you're going to want capacitors.

Except the weapon in the game wasn't called a Gauss Rifle and the one in Traveller was. So it tells me the guy knew exactly where his idea actually came from but wanted the increased pageviews from a videogame tie in. Sometimes it helps to read the article.:)

You mean the article where he explicitly says his inspiration was a weapon from Crysis 2?

Gauss Rifle was the term used in Traveller, but not only in Traveller, it's mentioned in many other places including games, which is why I knew exactly what a Gauss Rifle was despite never having heard of Traveller.

So it doesn't actually tell you that Traveller was his inspiration at all.

And the guys who created Crysis got the idea from someone earlier who got the idea from someone earlier and so on. As soon as someone figures out how to perfect a ceramic based superconductor, these things will be common place. And will be very light and orders of magnitude more powerful. Right now at 7.5 pounds this one isn't that heavy considering it is home built. I know it's supposed to be a sort of pistol, but I used to lug around a 10 pound FN rifle. 7.5 pounds isn't so bad. And in comparison to a Ste

I know the Gauss Rifle has been a standard piece of weaponry in the Mechwarrior series from the BattelTech universe.

Still have fond memories of configuring MW4MERCS/VENG "pop-tart" "gauss-boat" sniper 'mechs (mech with jump-jets and loaded with all the gauss-rifles it can carry, maybe with an additional laser or two if room permits) that could suddenly pop up over the crest of a medium-distant hill/ridge and salvo-fire all weapons and ruin an unwary opposing mechwarrior's whole day.

Nite Owl was inspired by Blue Beetle, the original Charlton character Alan Moore wanted to write about. And the Gauss rifle or coil gun was invented and built in the 60s by Kristian Birkelan, which then inspired 70s SF I guess.

No. A coilgun [wikipedia.org] and a railgun [wikipedia.org] are different. The fact that a lot of sci-fi describes the physics of coilguns but calls them railguns causes a lot of misconceptions. But it's pretty simple, seeing as one uses coils and the other uses rails (who'da thunkit?).

Coilguns actually are good at shooting conductive pellets, since the induced current creates an opposing field and force. The best pellets are often iron cored with a thick copper sheath, giving the best of both worlds.

Some designs have non-ferromagnetic projectiles, of such as aluminum or copper, with the armature of the projectile acting as an electromagnet with internal current induced by pulses of the acceleration coils.

are we talking starcraft gauss rifle? fallout 3/new vegas gauss rifle? it looks like it belongs in dead space. it also looks like a glorified version of this http://www.youtube.com/watch?v=QPciBQnZw3c [youtube.com]

But with chemicals you are limited to the amount of powder you can put in a cartridge, while electric guns can have big batteries attached to them. I still don't think portable electric guns are near, but on a stationary platform with lots of electricity (like ships) they could be effective.

What would a big gun on a ship really do though? The biggest guns modern ships mount are the phalanx anti-air/anti-missile weapons, attacks are performed via missiles or airplanes. What would a railgun add? Increased projectile speed may help to build better flaks but if you've got THAT much power and proper aiming then can't you just build a laser?

Indirect Artillery-style Over-The-Horizon firing, with no anti-missile counter measures available to stop it? Being able to spread the acceleration along the barrel instead of requiring a single big explosion might be an advantage somewhere as well (presumably in materials engineering required). Also possibly useful for the rail-gun style underwater shots, where lasers are ineffective, though I'm not sure on the advantage over torpedoes -- possibly speed?

As with electric cars and aircraft, the power density of boring, smelly chemical fuels are just stubbornly competitive with electric tricks...

Not really. Electric cars and aircraft have low energy density (aka specific energy aka energy per unit mass), but the power density is outrageously high, even if this particular coilgun specemin is uninspiring.

Aye. Making the tube longer won't help muzzle velocity much if the propulsion system is magnetic instead of expanding gas.
100 m/s is 360 kph, or pretty damn low for a projectile. And this thing requires a bunch of Li-Ion batteries, and needs a recharge after 50 shots? So, in effect, it's cute toy, but the applications are going to be limited to situations where boring, smelly chemical fuels are simply not an option, but a heavy, electric beast is.

boring, smelly chemical fuels are simply not an option, but a heavy, electric beast is.

Fundamentally a battery basically is a boring smelly chemical fuel, its just in a can and hopefully doesn't make much smoke while it releases its chemical energy. There are some interesting thermodynamic issues with chem fuels and temperatures which can sometimes make a battery reaction more efficient (why the shuttle uses fuel cells instead of a little internal combustion engine to generate electricity, etc). Another reason chem propellants suck is the projectile can never, ever travel faster than the sp

Another reason chem propellants suck is the projectile can never, ever travel faster than the speed of sound of the column of compressed high pressure gas in the barrel, but at least in theory theres no reason an infinitely complicated coil gun couldn't launch stuff at any ridiculous speed.

I may be misunderstanding you, but it sounds like you're saying that bullets can't travel faster than the speed of sound? If so, this information is incorrect... Most rifle rounds can exceed the speed of sound quite easi

I don't believe that the author is saying that a bullet can't travel faster than the speed of sound outside the barrel (where pressure, at presumably one atmosphere, is relatively low), but that it cannot travel faster than the speed of sound in the barrel at the time the bullet is fired (where the pressure is much higher than 1 atmosphere). As I recall, sound travels through gas much faster when said gas is compressed than it does when that gas is not compressed (note also that sound travels much faster t

It's not just rifle rounds. Even a.22 LR pistol has no problem breaking the sound barrier.

You are correct with suppressors though. The supersonic "crack" of a projectile is quite loud, and suppressors do nothing to reduce this, except for a small decrease in muzzle velocity. Still, a suppressed rifle is much quieter than an unsuppressed rifle.

The speed of sound within the barrel is dependent on the temperature of the hot gas behind the projectile, not the pressure. As such the projectile cannot exceed the speed of sound of the gas within the barrel. Now since the speed of is dependent on the molecular weight of the gas and the temperature (not pressure) the speed of sound within the barrel is higher than the speed of sound outside of it. A good explination of this can be found on the Wikipedia page about light gas guns in the design physics [wikipedia.org] sect

Another reason chem propellants suck is the projectile can never, ever travel faster than the speed of sound of the column of compressed high pressure gas in the barrel, but at least in theory theres no reason an infinitely complicated coil gun couldn't launch stuff at any ridiculous speed.

That "speed of sound in the barrel" is interesting to think about... the pressure is so high in the barrel that the speed of sound might be 2 or 3 times, maybe even more, than the speed of sound in sea level air.

Almost right. The speed of sound is dependent on the temperature and molecular weight of the gas, but not on the pressure directly. While there is some play with the adiabatic ratio, if you compress a gas and then chill it back to the same temperature but higher density, the speed of sound will not have significantly changed.

Now there are some ways around this issue. Temperature is a big limiting factor, since you can only heat the gas so far before your materials fail. However, you are free to change t

I have no idea how much damage these bullets would do at this speed but a coil gun may work as a silent delivery system for sub-sonic rounds since there are no mechanic parts that would cause a loud snap and keeping the projectile below the speed of sound would prevent the sonic boom as well. Of course a silent gun isn't terribly great if you can't conceal it at all.

I suspect that electromagnetic projectile propulsion gets a great deal more interesting if you enjoy the benefit of having nothing but a couple of meters of superconductive feed rail between you and your nuclear reactor(s), which I assume is why the navy is messing around with them. It's in the smaller scale areas where little packets of chemicals have been reliably killing people for several centuries now, and microfusion cells are still a Fallout 3 inventory item...

The only thing reactors are put on these days are carriers, and submarines. The US Navy would be putting them on gas turbine powered ship, where there would be a large electric generator attached to the propulsion turbines.

The battery size reflects the "clip" size. You'll be lucky if your battery size/weight is much smaller than the ammo it flings for a bunch of basic chemistry reasons. A battery the size of a truck trailer would be able to fling a volume/weight of ammo about the size of a truck trailer, either all at once or more likely eventually. In other words the energy density of chemical batteries is never going to be a whole heck of a lot better (like orders of magnitude, not the smallest decimal point) than the energy density of smokeless powder. Hence the intense interest in hypersonic projectiles. I suppose if you had a nuclear aircraft carrier or nuclear powered submarine to power it, then...

The velocity reflects the weight and number of the coils. Something that is pretty wimpy compared to a slingshot is about the most a human can handle. If you insist on hypersonic velocities its going to be immensely huge and probably quite inefficient as a tradeoff making the whole weapon system fairly useless.

Your budget reflects the total projectile energy via capacitor bank size. Something light enough you can pick up and an individual might be able to afford makes for the worlds wimpiest pellet gun, not much more than airsoft really. If you insist on blowing up a tank, you'll need a truck trailer full of capacitors costing about as much as a house. Capacitors are a really awful way to store energy, but the only way to release the energy quick enough for hypersonic power. If you get serious, internal resistance and crushing magnetic forces and strange resonant effects become a big problem (no longer able to treat the cap as the simple AC/DC electronics 101 simplification of a perfect device anymore)

Usually the limiter for the home builder is triggering followed by power supplies. Whats most likely to stop you is finding a big and bad enough set of SCRs or whatever to handle triggering or if you try mechanical like this guy you end up accidentally building a arc welder, second your average noob is mystified at how to generate more than a couple hundred volts without spending lots of money or getting killed or blowing up the trigger system. If they succeed at that, the next limiter is usually the spectacular cost of high voltage low resistance high capacity capacitors... any 1 or 2 of the 3 isn't going to do, and maxing out all 3 is going to be very expensive. Assuming you pull that off, coils are pretty simple, as are batteries.

In all honestly, the "coil gun" concept really doesn't make a whole lot of sense. Electromagnetic coils can't be instantaneously turned on and off. The magnetic reluctance of your coil means it takes some amount of time for the field to come up to strength as power is applied, and some amount of time for the field to dissipate after power is removed. Even if you had tons of stages, and those stages were perfectly timed, the reluctance means that at the switching speeds you need to operate at, you're gett

TFA: Fortunately, he has no plans on developing it commercially, or on telling other people how to make one of their own.

Capacitors, em coils, pressure sensors... you pretty much already told us how to build it. Of course, anyone with an IQ above room temperature could have worked that out from the descriptions in the various games that employ similar weapons. I personally would have gone with something other than pressure sensors to trigger the next coil -- wear/tear, added drag, etc. -- but to each his ow

For even more 'awesome but impractical' bonus points, I suspect you could modify this so that the laser sight actually shines out of the barrel. Repurpose the mirror-flipping mechanism out of an old SLR camera.

With 3X the mass and 1/3rd the speed it would have the same momentum. Granted, the power, as in energy, delivered would be less, but with a weapon you might be more concerned about momemtum. A small high-energy particle might pass completely through a target while doing minimal damage. But a larger particle with less energy might be able to do more damage, or at least have a greater chance of knocking the target down, often referred to as "stopping power". Consider a gun battle between two beligerents,

Everything you said is true. But don't get the idea that smaller, high-velocity bullets are useless - otherwise, we'd still be using 20mm musket balls. Bullets since the Minie ball in the American Civil War have been designed to offset their lack of stopping power with fragmentation and wounding effects - your hit through the shoulder isn't just going to zip in and out. It's going to zip in, shatter, then tear out, taking many times its volume in flesh with it. And the smaller, lighter ammo and easier r

That's why modern rifle rounds are unstable, but spin stabilized. Low weight and high velocity means they have good range and accuracy, as well as some ability to penetrate armor. Instability means when they are disrupted by some kind of resistance, like a human, they tend to yaw violently and then fragment. Technology to provide all the lethality of a hollow point bullet, but without violating the Geneva Convention.

A bit of research tells me that 45 ACP rounds are about 10-15 grams. The video says the railgun projectiles are 5.6 x 16 mm.. I'm assuming both are mm, then, which would mean a perfect cylinder would have 0.394 cm cubed of mass. Most steel seems to be about 7.5 gram per cm3, so that'd be about 3 grams.. a little less, because it's not a cylinder.

It has 1/5th the mass, and 1/3rd the velocity. Kinetic energy would be.. what. 1/75th?

It's not excessive. The energy stored and released by the capacitors in this guys rail gun is nowhere near as much as the amount released by the gun powder in a bullet. Assuming those are 100uf 400V capacitors, you're talking about 1600J, a fair amount of that would be lost as heat in the internal resistance of the capacitor and the resistance of the coils. The projectile carries around 10 - 15J of energy.

I just took one look at the picture and thought the guy made it with 8 iPads. I felt a sigh of relief to know that no one would've been that stupid, but also paradoxically felt bummed that they weren't.